This invention relates to medical prostheses, particularly those medical prostheses used for a breast or testicular prosthesis.
Silicone-gel implants have fallen into disfavor in recent years which has created a need for new implants that can be used as medical prostheses. Medical prostheses from a safety standpoint should be chemically inert, noninflammatory, nonallergenic, and noncarcinogenic. In the case of breast implants, they ideally should also simulate the viscoelastic properties of the normal human breast, and be radiolucent to mammography. It is further important that breast implants create a natural "feel" and desirable aesthetics.
Much research has been directed toward finding alternative prostheses fitting this description. Although saline filled prostheses in large measure meet the criteria outlined above, saline prostheses create an unnatural feel and less than optical aesthetics. When implanted, for example, they tend to result in wrinkling of the overlying skin. In addition, Ersek et al. in U.S. Pat. No. 5,067,965 disclosed in column 1 that a prosthesis filled with saline alone undergoes accelerated breakdown of the outer shell of the prosthesis due to friction of the inner shell rubbing against itself. Due to this accelerated breakdown, the implants must be surgically replaced periodically, typically on the order of every four to five years. Ersek et al. further state that saline is a poor lubricating agent. Because of the relatively high amount of motion of the saline in the implant, the implant is also prone to fold-crease failure resulting in a rupture of the implant.
There is also a continuing need for implants that are radiolucent. It is therefore desirable that breast prostheses not unduly interfere with the ability to perform X-ray mammograms. Breast protheses that are radiographically dense can be serious impediments to effective mammography.
In addition, implants filled with saline alone may oftentimes not be usable for breast cancer patients who have undergone radiation therapy. Since the radiation weakens the tissue, the movement of the saline in the implant may be very painful to the patient such that the saline filled implant is not used.